Is it common for the oil pick up tube o ring go bad in the clk320

What is your question?

The engine is making a nop nop nop noise. You can hear it when you put your ear by the drivers front tire. Or when it's warm 80 degrees plus you can hear it with the door open. Kinda sounds like a diesel. Already replaced the harmonic balancer tensioner pulley checked the lifters. I'm down to transmission flex plate or oil pick up tube o ring. Tranny works fine. Changes gears like supposed to very smooth no delays. So I'm thinking the other.

What makes this problem better or worse?

Worse when engines warm. Not really there when cold. In park or neutral. Only drive and reverse

How long has your 2002 Mercedes-Benz CLK320 had this problem?

16 months